Based on the development of metal organic chemical vapor deposition, molecular beam epitaxy, and the like of gallium nitride (GaN), red, green and blue light emitting devices (LEDs) that have high luminance and realize white light have been developed.
Such LEDs do not contain environmentally harmful materials such as mercury (Hg), which is used in existing luminaires, such as incandescent lamps and fluorescent lamps and thus exhibit excellent eco-friendliness, long lifespan, and low power consumption. Thus, these LEDs are replacing conventional light sources. A core competitive factor in such LEDs is to achieve high luminance using chips with high efficiency and high power output and packaging techniques.
To realize high luminance, it is important to increase light extraction efficiency. To increase light extraction efficiency, research into various methods using flip-chip structures, surface texturing, patterned sapphire substrates (PSSs), a photonic crystal technology, anti-reflection layer structures, and the like is underway.
FIG. 1 is a sectional view of a general LED.
Referring to FIG. 1, the LED includes a plurality of light emitting cells D1 and D2, and the light emitting cells D1 and D2 respectively include a substrate 10, light emitting structures 20 and 40, first electrodes 32 and 52, second electrodes 34 and 54, a passivation layer 60, and a metal connection layer 70.
The light emitting structures 20 and 40 respectively include n-type semiconductor layers 22 and 42, active layers 24 and 44, and p-type semiconductor layers 26 and 46 that are disposed on a substrate 10. The metal connection layer 70 electrically connects the first electrode 32 of one (i.e., light emitting cell D1) of the adjacent light emitting cells D1 and D2 to the second electrode 54 of another one (i.e., light emitting cell D2) of the adjacent light emitting cells. In this regard, the passivation layer 60 electrically separates the metal connection layer 70 from the light emitting structure 40 of the light emitting cell D2, electrically separates the adjacent light emitting cells D1 and D2 from each other, and electrically separates the n-type semiconductor layer 22 of the light emitting cell D1 from the metal connection layer 70.
The general LED illustrated in FIG. 1 further requires a separate process for forming the passivation layer 60 and thus manufacturing time and cost of such LEDs increase.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.